An Omni-directional treadmill (ODT) that allows a user to traverse in the X, Y, and theta directions has been described as the Holy Grail for virtual reality systems. Among other things, the ODT can function as a walking simulator when used in combination with virtual reality environments for activities such as gaming, military simulations, or evacuation simulations. Other examples of where an ODT may be used include laboratories for human motion studies, in perceptual studies for psychology experiments, in a gym as indoor exercise equipment, as language immersion systems, and as conveyors for manufacturing, just to provide some examples.
The company Virtual Space Devices, Inc. has an existing commercial ODT product. However, the available model only allows the user to move in two directions. The Virtual Space ODT uses a regular treadmill that includes 3400 rollers in the lateral direction to allow the user to slip sideways, and to move in two directions. However, the Virtual Space ODT is very complicated, noisy, and does not allow for natural movements. For example, the sideways motion feels icy, and the user has to wear a harness in case he or she slips.
The Virtual Reality Laboratory at University of Tsukuba developed an ODT called the Torus treadmill. The Torus treadmill uses a torus-shaped surface to build the locomotion interface. This treadmill consists of ten normal belt conveyers, which are connected side by side and driven in a perpendicular direction to simulate an infinite surface. The position of the walker is fixed in the real world by computer-controlled motion of the conveyers. This product requires many motors, and the motion of the user must be sensed using a vision system.
The US Army is funding the development of a locomotion simulator called the OmniTrek™, which allows motion in two directions as well as stair climbing. It is a complex device that involves two servo controlled robot arms to catch the user's feet. Another ODT is the Sarcos Treadport™, which was developed in 1995 and is based on the standard one-directional treadmill. The user of the Sacros Treadport™ must be monitored and constrained by a mechanical attachment to the user's waist. The user can walk, jog, and kneel, and the incline of the treadmill can be adjusted to simulate hills. However, the physical movement is constrained to one direction.
Other inventions include a giant sphere to walk inside, a walking surface consisting of hundreds of miniature balls, an air-walker, a treadmill that rotates, and walking slippers. However, the current systems all have at least one or more shortcomings that include: restrictive motion, being limited to upright motion, noisy, complicated, requires a tracking system, and, during acceleration transitions, having a tendency of causing the user to slip or fall.
Preferably, an ODT needs a surface that reacts to movement in any direction so that the user remains in a small set area. As discussed above, some ODTs incorporate rollers in the sideways or transverse direction to allow the user to slip back to the center of the ODT. However, the disadvantage with this design is that the slippery motion does not allow the user to walk freely. The ODT with rollers also tends to leave the user with the feeling of stepping and then sliding, not a natural walking motion.
Accordingly, there is a need for an ODT that is simple to operate, that provides smooth accelerations and transitions, that is relatively quiet, and that can control the damping or stiffness in any planar direction. Furthermore, there is a need for a method of making the ODT with all the advantages discussed.